Alaskan landscape evolution and glacier change in response to changing climate

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1 Alaskan landscape evolution and glacier change in response to changing climate Following the publication of two pictures comparing the length of the Muir Glacier in Alaska, USA in the June 2005 issue of Weather, Dr Bruce Molnia of the US Geological Survey has kindly sent us a series of similar images, showing the changes during the past century of various glaciers. Almost all have reduced in size, although there are notable exceptions. Correspondence to: Dr Bruce F Molnia, US Geological Survey, 926A National Center, Sunrise Valley Drive, Reston, Virginia bmolnia@usgs.gov USGS Photo Library Photograph Grant 208 Fig. 1 View north from near the head of Harvard Arm, College Fiord, Prince William Sound, Chugach National Forest, Alaska. The pair document significant changes that have occurred during the 91 years between 1 July 1909 and 3 September The earlier photograph (left) shows Harvard Glacier at the head of the fiord with Radcliff Glacier, one of its largest tributaries flowing into it at the right of centre, Baltimore Glacier, a retreating hanging glacier is at the left side of the photo. If any vegetation is present it is on the hill slopes above the fiord. The right-hand photograph, taken in 2000, documents the continuing advance of Harvard Glacier, which has completely obscured the view of Radcliff Glacier. Baltimore Glacier has continued to retreat and thin. Alder has become established on the hill slopes, but is difficult to see from the photo location. Harvard Glacier has advanced more than 1 km since USGS Photo Library Photograph Wright 333 Fig. 2 View north from a position on Triangle Island, Queen Inlet, Glacier Bay National Park and Preserve, Alaska, showing the changes that have occurred to Carroll Glacier and upper Queen Inlet during the 97 years between August 1906 and 7 September The 1906 photograph (left) shows the calving terminus of Carroll Glacier sitting at the head of Queen Inlet. No vegetation is visible. The 2003 photograph, on the right, shows that the terminus of Carroll Glacier has changed to a stagnant, debris-covered glacier that has significantly thinned and retreated from its 1906 position. The head of Queen Inlet has been filled by sediment. An examination of early twentieth-century nautical charts suggests that the sediment fill exceeds 120 m. Note the developing vegetation on the island.

2 Alaskan landscape evolution USGS Photo Library Photograph Grant 132 Fig. 3 View north-west from near the head of Holgate Arm, Aialik Bay, Kenai Fjords National Park, Alaska. The pair document significant changes that have occurred during the 95 years between 24 July 1909 and 13 August The photograph taken in 1909 (left) shows Holgate Glacier, a tidewater glacier at the head of the fjord with Little Holgate Glacier, one of its former tributaries, located to its left. Little Holgate Glacier terminates at the shoreline. No vegetation is present at the head of the fjord. The right-hand photograph documents the continuing retreat of both glaciers. "Little Holgate Glacier" has separated into several smaller ice masses and Holgate s terminus, while still tidewater, has retreated from the field of view. Alder has become established on the hill slopes. USGS Photo Library Photograph Capps Fig. 4 View north from a position near the retreating un-named valley glacier that forms the East Fork of the Teklanika River, Denali National Park and Preserve, Alaska. The pair document changes that have occurred during the 85 years between June 1919 and August The 1919 photograph (left) shows the then retreating, debris-covered terminus of East Fork Teklanika Glacier with an elevated lateral moraine on its west (left) side. Small tundra plants are the only identifiable vegetation. The photograph on the right documents the continued thinning and retreat of East Fork Teklanika Glacier. The glacier has retreated more than 300 m since 1919, retreating at an average rate of ~ 4 m per year. USGS Photo Library Photograph Grant 144 Fig. 5 View north from about 8 km north of the mouth of McCarty Fjord, Kenai Fjords National Park, Alaska. The pair document significant changes that have occurred during the 95 years between 30 July 1909 and 11 August The left-hand photograph shows the west side of the terminus of the then retreating McCarty Glacier, a tidewater glacier. Little, if any vegetation is present in the photograph. The right-hand photograph documents the retreat of McCarty Glacier from the field of view, a retreat of more than 16 km. Dense, diverse vegetation, featuring spruce, has become established on the hill slopes. 85

3 Alaskan landscape evolution Field photograph # Fig. 6 View south-west from the same position adjacent to Lamplugh Glacier showing the changes that have occurred at the lower end of Lamplugh s inlet during the 62 years between August 1941 and 8 September The left-hand photograph shows the calving terminus of Lamplugh Glacier extending to within a half mile of the photo point. No vegetation is visible. The photograph on the right shows that the terminus of Lamplugh Glacier is about 500 m forward of its 1941 position. However, glacial sediment on the bedrock ridge in the foreground indicates that Lamplugh Glacier had advanced beyond the photo point at some time during the interval between photographs, probably in the late 1960s. Note the isolated vegetation. USGS Photo Library Photograph Gilbert 276 Fig. 7 View north from the same shoreline location near Muir Point, Muir Inlet, Glacier Bay National Park and Preserve, Alaska, that document changes that have occurred during the 104 years between June 1899 and September The photograph on the left shows the calving terminus of Muir Glacier extending almost to the photo point and the absence of any identifiable vegetation. On the right, the photograph shows the disappearance of Muir Glacier from the field of view. The distant glacier at the extreme right is Rigs Glacier, more than 30 km to the north. Note the extensive vegetation that has developed. 86 USGS Photo Library Photograph Paige 731 Fig. 8 View north from about the same offshore position of Toboggan Glacier, Harriman Fjord, Prince William Sound, Chugach National Forest, Alaska. The pair document significant changes that have occurred during the 91 years between 29 June 1909 and 4 September The earlier photograph (left) shows that Toboggan Glacier was thinning and retreating, and was surrounded by a large bedrock barren zone. Minimal vegetation existed on the fjord-facing hill slopes. By 1909, the terminus appears to have thinned to about 50% of its former depth. The later photograph (right) shows the continuing thinning and retreat of Toboggan Glacier. The former tributary located on the north (left) side of the glacier has also thinned and retreated significantly. Note the extensive vegetation that has developed on the beach and at the glacier s margins.

4 Alaskan landscape evolution Fig. 9 View north from the same shoreline location in upper Muir Inlet, Glacier Bay National Park and Preserve, Alaska, showing the changes that have occurred during the 27 years between 15 August 1976 and 8 September The earlier photograph (left) shows the calving terminus of Muir Glacier extending the width of the fjord. A thinning tributary flows in the valley to its north. Aside from algae growing on a lighter coloured dyke, there is no vegetation visible in the photograph. By 2003, Muir Glacier had retreated out of the field of view (right). The two small cirque glaciers at the upper left have probably not been connected to Muir glacier. Muir Glacier has retreated about 10 km to the north. Note that vegetation is beginning to develop. USGS Photo Library Photograph Grant 131 Fig. 10 View south-west from about the same shoreline location of Pedersen Glacier, Aialik Bay, Kenai Fjords National Park, Alaska. The pair document significant changes that have occurred during the 95 years between 23 July 1909 and 13 August The left-hand photograph shows the north side of the then retreating terminus of Pedersen Glacier, grounded on the beach above tidewater. Little, if any, vegetation is present in the photograph. The later photograph (right) shows that Pedersen Glacier has retreated from the field of view, about 1.2 km. Diverse vegetation, featuring alder and spruce, has become established on the hill slopes and on the elevated ground of the former terminus. Beach vegetation is also becoming established. USGS Photo Library Photograph Gilbert 278 Fig. 11 A pair of north-eastward-looking photographs, both taken from the same shoreline location near Muir Point, Muir Inlet, Glacier Bay National Park and Preserve, Alaska, that document changes that have occurred during the 104 years between June 1899 and September The earlier photograph (left) shows the calving terminus of Muir Glacier, near its confluence with Adams Glacier. No vegetation is visible. The later photograph (right) shows that the Muir and Adams Glaciers have both retreated from the field of view. Muir Glacier has retreated more than 40 km north. Note the extensive vegetation that has developed. 87

5 Alaskan landscape evolution USGS Photo Library Photograph Wright 333 Fig. 12 Looking north-west, several hundred metres up a steep alluvial fan in a side valley on the east of Queen Inlet, Glacier Bay National Park and Preserve, Alaska, showing the changes that have occurred to Carroll Glacier and upper Queen Inlet between August 1906 and 21 June The earlier photograph (left) shows the calving terminus of Carroll Glacier at the head of Queen Inlet. No vegetation is visible. The later photograph (right) shows that the terminus of Carroll Glacier has changed to a stagnant debris-covered glacier that has significantly thinned and retreated. The head of Queen Inlet has been filled by sediment. An examination of early twentieth-century nautical charts suggests that the sediment fill exceeds 120 m. Note the developing vegetation on the sediment fill. USGS Photo Library Photograph Grant 143 Fig. 13 A pair of photographs looking north-east from about 8 km north of the mouth of McCarty Fjord, Kenai Fjords National Park, Alaska. The pair document significant changes that have occurred during the 95 years between 30 July 1909 and 11 August The earlier photograph (left) shows the east side of the terminus of the retreating McCarty Glacier, a tidewater glacier. Little, if any, vegetation is present on the upper slopes, but beach grass is present in the foreground and trees are present on the back beach to the right. The photograph on the right shows part of the McCarty Glacier, more than 16 km up the bay. Dense, diverse vegetation, featuring alder, willow and spruce, has become established on the hill slopes and back-beach areas. Note the beach grass in the foreground. 88 Alaska State Library Photograph by Winter and Pond Fig. 14 A pair of photographs looking south-west, from the same shoreline position near Muir Point, Muir Inlet, Glacier Bay National Park and Preserve, Alaska, showing changes that have occurred between June 1895 and 28 August The photograph on the left shows the area adjacent to the retreating terminus of Muir Glacier, about 400 m to the north (right). No vegetation is visible. On the right, the recent photograph shows that diverse dense vegetation has developed on all but vertical surfaces. Calcareous organisms have populated the Intertidal zone and are attached to most of the glacier beach cobbles. Muir Glacier has retreated more than 40 km. doi: /wea